Impermeable base materials such as plastic films are used for industrial purposes such as advertisements and signages in order to improve durabilities such as light resistance, water resistance, and wear resistance. There have been developed various inks intended for use on the impermeable base materials.
Widely used among such inks are solvent-based inks using an organic solvent as a vehicle and ultraviolet-curable inks mainly made of a polymerizable monomer. However, there are concerns that the solvent-based inks may become hazardous to the environment through solvent vaporization. The ultraviolet-curable inks may be limited in selection of polymerizable monomers to be used in terms of safety.
Hence, there have been proposed water-based inks that are lowly environmentally hazardous and can be recorded directly over impermeable base materials (see, e.g., PTLs 1 and 2).